Photographic color developing solutions containing p-toluenesulfonic acid salts of p-phenylenediamines

ABSTRACT

The p-toluenesulfonic acid salts of certain p-phenylenediamine color developing agents have been found to possess extraordinarily and unexpectedly high solubility in aqueous alkaline solution. Thus, extremely concentrated solutions of these materials can be prepared to provide developer &#39;&#39;&#39;&#39;concentrates&#39;&#39;&#39;&#39; which are extremely economical to ship and working developer solutions which possess abnormally high developing agent concentrations and which are therefore capable of producing unusually high dye density levels in very short periods of time. Specifically preferred among these pphenylenediamine salts are the di-p-toluenesulfonic acid salts of 3-alkyl and 3-alkoxy N-alkyl-N-alkoxyalkyl-p-phenylenediamine developing agents.

United States Patent [191 Schellenberg et al.

PHOTOGRAPHIC COLOR DEVELOPING SOLUTIONS CONTAINING P-TOLUENESULFONIC ACID SALTS OF P-Pl-IENYLENEDIAMINES Inventors: Dietmar Schellenberg; Richard L.

Bent, both of Rochester, NY.

Assignee: Eastman Kodak Company, Rochester, N.Y.

Filed: Dec. 3, 1971 Appl. No.: 204,725

References Cited UNITED STATES PATENTS 4/l972 Bent et al 96/66 R 4/l972 Bent et al 96/66 R June 11, 1974 Primary Examinerl. Travis Brown Attorney, Agent, or Firm-Alfred P. Lorenzo 5 7 ABSTRACT The p-toluenesulfonic acid salts of certain pphenylenediamine color developing agents have been found to possess extraordinarily and unexpectedly high solubility in aqueous alkaline solution. Thus, extremely concentrated solutions of these materials can be prepared to provide developer concentrates" which are extremely economical to ship and working developer solutions which possess abnormally high developing agent concentrations and which are therefore capable of producing unusually high dye density levels in very short periods of time. Specifically preferred among these p-phenylenediamine salts are the di-p-toluenesulfonic acid salts of 3-alkyl and 3-alkoxy N- alkyl-N-alkoxyalkyl-p-phenylenediamine developing agents.

9 Claims, No Drawings PHOTOGRAPI-IIC COLOR DEVELOPING SOLUTIONS CONTAINING P-TOLUENESULFONIC ACID SALTS OF P-PI-IENYLENEDIAMINES This invention relates to color photography and more particularly to color photographic developing agents which are capable of forming unusually highly concentrated aqueous alkaline solutions and hence, provide faster rates and shorter times of color development.

In the process of color photography, it is known to use p-phenylenediamine developing agents in conjunction with couplers to produce colored images. A summary of this process is described by Thirtle et al., Encyclopedia of Chemical Technology, VOl. 5, pp. 812-845 (1964), John Wiley & Sons, Inc. The color developing agent is oxidized by the silver halide in the presence of a latent image ina photographic element to produce silver metal and oxidized color developing agent. The oxidized color developing agent then couples with color-producing compounds present to produce a dye image-wise with respect to silver development.

Color development of the differently sensitized emulsion layers in color photographic elements containing nondiffusible couplers is advantageously performed in a single color development step to produce a color negative image reproduction when this development step is the first development step, or to produce a color reversal image if a negative black-and-white development step is used followed by a step in which the residual unexposed and undeveloped silver halide is made developable and then color developed. In reversal color photographic elements that do not contain nondiffusible couplers, diffusible couplers are used in the aqueous alkaline color developer solutions that are used to selectively color develop one silver halide emulsion layer at a time. The reversal processing of such a multicolor, multilayer element (containing no incorporated couplers) requires a negative black-and-white process followed by a step in which residual unexposed and undeveloped silver halide in each emulsion layer is selectively made developable, then that layer is color developed with a color developing solution containing a diffusible coupler that forms a nondiffusible dye that is complementary in color to the light-sensitivity of that layer, then the unexposed and undeveloped silver halide in a second emulsion layer is selectively made developable and color developed with another color developing solution containing a diffusible coupler that forms a nondifiusible dye that is complementary in color to the light-sensitivity of that layer. Following completion of the color development, the silver and any residual silver halide are removed by silver bleaching and then fixing the photographic element. In any such color process, it is important that as large as practical and possible a quantity of color developing agent be brought into contact with the exposed, black-andwhite developed etc. element within the shortest possible period of time so that maximum density dye images are produced with optimum efficient usage of the silver present in the photographic element in the minimum amount of time.

Also, in recent years, in order to eliminate the need for complex, expensive mixing equipment at the processors location, it has become the custom in the trade to provide processing chemicals in the form of concentrated aqueous solutions which, while they are easier to dissolve or dilute with water than the dry processing chemicals, provide similar results. This dissolution of dry chemicals often required several hours of intense mixing with expensive equipment, and somtimes resulted in solutions containing substantial amounts of undissolved solute which rendered practical usage thereof impossible.

In view of the costs of shipping such concentrates attempts have continuously been made to reduce the amount of water which had to be shipped in the concentrates and consequently to increase the concentration of the working chemicals (i.e. developer, bleach, fix, etc.) to the highest practical levels which provide a stable solution.

Thus, in the photographic arts there has existed a definite need and desire for, among other things, more concentrated solutions of p-phenylenediamine color developing agents which provide faster rates of color development and hence shortened color development times for color photographic elements and simultaneously permit the preparation of extremely concentrated solutions of color developer for shipment from the supplier to the processor customer.

Among the prior art suggesting methods for increasing the solubility of p-phenylenediamine developing agents are a large number of references which suggest the formation of the inorganic e.g. I-ICl salts of such compounds. More recently attempts to increase the solubility of these materials have been directed to the formation of organic salts thereof. Among this art is US. Pat. No. 2,618,558 to Vittum et al., which suggests the use of a benzene sulfonate of the formula:

l SOzM SUMMARY OF THE INVENTION It has now been discovered that the p-toluenesulfonic acid salts of p-phenylenediamine color developing agents are unusually soluble in aqueous alkaline solutions of thetype used as working solutions in the color development of multilayer color photographic elements and as concentrates for the shipping of such color developers from the chemical manufacturer to the processor.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention the p-toluenesulfonic acid salts of color developing agents having the formulas:

II, R

wherein R, and R are alkyl groups having from 1 to 4 carbon atoms i.e. methyl,-ethyl, propyl, butyl etc., hydroxy alkyl groups having from 1 to 4 carbon atoms i.e. hydroxy methyl, hydroxy ethyl, etc., or alkoxy alkyl groups having from 2 to 8 carbon atoms i.e. methoxy methyl, methoxy ethyl, ethoxy methyl, ethoxy ethyl etc. and R is an alkyl or alkoxy group having from 1 to 4 carbon atoms have been found to have unusually and unexpectedly high solubility in aqueous alkaline solutron.

The p-toluene sulfonic acid salts of these developing agents are generally represented by the following generic formula: v

(II) R1 wherein n is either 1 m2 and R,, R and R are all as described above.

Specifically preferred among this class of materials are those having the following generic formula:

wherein m is an integer of 2 to 4; R is an alkyl group having 1 to 4 carbon atoms, e.g. methyl, ethyl, propyl,

' butyl, etc. and R is an alkyl group having from 1 to 4 carbon atoms, e.g. methyl, ethyl, propyl, butyl etc., or an alkoxy group having from 1 to 4 carbon atoms, e.g. methoxy, ethoxy, propoxy, butoxy. These compounds have been found to be extremely and unexpectedly more soluble in aqueous alkaline solutions that even the toluenesulfonic acid salts of other pphenylenediamine developers which also demonstrate improved solubility. Thus, the formulation of even more concentrated concentrates of these materials in aqueous alkaline solution is possible. This provides working color developer solutions which yield higher development rates due to the higher developing agent levels. Furthermore, color developing agents falling within the aforementioned generic Formula I possess other substantial processing advantages which will be discussed in greater detail hereinafter and which are described in substantial detail in US. Pat. application Ser. No. 94,992 filed Dec. 3, 1970 and issued Apr. 25, 1972 as US. Pat. No. 3,658,525 andapplication Ser. No. 94,993 filed Dec. 3, 1970 and issued Apr. 18, 1972 as U.S. Pat. No. 3,656,950. These applications are incorporated herein by reference. Furthermore, the high solubility of these salts permits the use of higher developer concentrations in PODS" of the type used in the picture in-a-minute photographic system of the type described in US. Pat. Nos. 3,537,851 and 3,537,852 to Bloom issued July 1, 1968. The advantages of having high volume of color developer present in an extremely small amount of solvent in these-and other photographic systems will of course be readily apparent to those skilled in this art.

Typical representative examples" of the preferred color developing agents of Formula I are the following:

.are prepared by reacting the appropriate w-alkoxyalkyl chloride or bromide with the appropriate N-ethyl- '3-alkyl-aniline or N-ethyl-3-alkoxyaniline. The tertiary anilines formed by this reaction are then either nitrosated or azo-coupled followed by catalytic hydrogenation to give the corresponding p-phenylenediamine. The p-toluenesulfonic acid salts of these materials are generally prepared by forming the 4-(2,5- Dichlorophenylazo) derivative of the pphenylenediamine derivative of Formula 1, reducing the azo dye and adding p-toluenesulfonic acid.

Specifically, the di-p-toluenesulfonic acid salt of Preferred Color Developing Agent 3 is advantageously prepared by the following sequence of reactions:

1. N-(B-Ethoxyethyl )-N-ethyl-3-methylaniline Amixture of 135 g (1 mole) of N-ethyl-3-aniline, 153 g (1 mole) of 2-bromoethyl ethyl ether (purified by treatment with sodium bicarbonate and distillation), 88.2 g (1.05 mole) of sodium bicarbonate, 1,100 ml of ethanol and 290 ml of water are refluxed for a total'of 64 hours. The ethanol is removed by distillation and the oil layer is extracted with ether; the ether extracts are dried and concentrated, followed by distillation of the residual oil under reduced pressure. After removal of the lower boiling foreruns, the fraction, b .p. 9295C/ 1mm (overheats readily) is collected. The yield of I is approximately percent.

11. 4- 2,5-Dichlorophenylazo )-N-( B-ethoxy-ethyl )-N,- ethyl-3-methylaniline A total of 44 g (0.27 mole) of 2, S-dichloroaniline is dissolvedin a mixture of 240 ml concentrated hydrochloric acid and 700 ml of water by heating with stirring on. a steam bath. When solution is complete, the reaction mixture is cooled with stirring to 5C, the hydrochloride salt precipitating out. A solution of 19 g (0.275 mole) of sodium nitrite in ml of water is added dropwise with stirring, keeping the temperature at about 5C. When complete, stirring is continued for another 20 minutes and the excess nitrous acid destroyed by the addition of sulfamic acid. The cold diazonium solution is filtered and at once added to a cold solution of 56 g (0.27 mole) of l in dilute hydrochloric acid. Considerably more water is added and with stirring a total of 250 g of sodium acetate is added to promote the coupling. After standing for a few hours, the azo dye is filtered off and at once recrystallized from approximately 1,000 ml of ethanol. This is followed by a second recrystallization from 900 ml of ethanol, filtering hot and cooling to about 25C. The yield of 11, mp. 74.5 755C, is 77 percent.

4-Amino-N-( B-ethoxyethyl )-N-ethyl-3- methylaniline, di-p toluenesulfonic acid salt (Developing Agent 3) Three grams of the azo dye, 11, is reduced on a Parr shaker using 300 ml of absolute alcohol and Raney nickel as catalyst. When complete, the catalyst is filtered off and washed on funnel with more ethanol. A solution of 3 g (0.0158 mole) of p-toluenesulfonic acid (hydrate) in 50 ml ethanol is added and the solution is then concentrated to dryness (partial vacuum). The semisolid is then slurried thoroughly with 35 ml of hot isopropyl alcohol, gradually becoming nicely crystalline. The mixture is cooled to about 25C and allowed to stand undisturbed overnight. The developer salt is filtered off and washed in a funnel with small portions of isopropyl alcohol. The yield of Developing Agent 3, mp. 214 216C, is approximately 70 percent. y

The di-p-toluenes'ulfonic acid salt of Color Developing Agent 5 is advantageously prepared similarly to developing agent (3), using N-ethyl-3-methoxyaniline and 2-bromoethyl methyl ether as starting materials. 111. N-Ethyl-3-methoxy-N-(B-methoxyethyD-aniline A mixture of 100 g (0.661 mole) of N-ethyl-3- methoxyaniline, 92 g (0.661 mole) of 2-bromoethyl methyl ether, 55.8 g (0.6665 mole) of sodium bicarbonate, 1,000 ml of ethanol and 280 m1 of water is refluxed for a total of 68 hours. The alcohol is removed under partial vacuum and the oil layer extracted with ether; the ether extracts are dried and concentrated. The residual oil is then distilled under reduced pressure. The yield of 111, bp 149 151C/8mm, is 35 percent. 1V. 4-(2,5-Dichlorophenylazo)-N-ethyl-3-methoxy-N- (B-methoxyethyUaniline This azo dye is prepared from 111 in exactly the same way as described for the preparation of the azo dye used for developing agent (3). The yield of 1V, m.p. 9496C (from ethanol), is approximately 73 percent.

The di-p-toluenesulfonic acid salt of 4-amino-N- ethyl-3-methoxy-N-(B-methoxyethyl )aniline (Developing Agent 5) Exactly 4.86 g (0.127 mole) of the azo dye, IV, is reduced on Parr shaker, using 300 ml of absolute alcohol and Raney nickel as catalyst. When complete, the catalyst is filtered off, washed on funnel with more alcohol. Av total of 4.84 g (0.0254 mole) of p-toluenesulfonic acid (hydrate) in 50 m1 of ethanol is added; no precipitate occurs and the solution is concentrated to dryness under partial vacuum. The gummy residue is then dissolved in a small quantity of absolute alcohol and a large excess of ethyl ether is added; the developer salt again comes out as a gum; the solution is cooled thoroughly (refrigerator) to precipitate the suspension and then the ether-alcohol layer is decanted. This treatment is repeated twice more to remove all of the regenerated 2,5-dichloroaniline. Finally, the developer salt is slurried thoroughly with ether only, gradually becoming crystalline; it is dried in a vacuum oven. The yield of Developing Agent 5, mp. 160 162C, is 62 percent.

The di-p-toluenesulfonic acid salt of Color Developing Agent 1 is made in a manner similar to the synthesis described for the corresponding acid salt of Color Developing Agent 5, excepting that an equimolar amount of N-ethyl-3-methylaniline is used in place of N-ethyl- 3-methoxyaniline. V

The di-p-toluenesulfonic acid salt of Color Developing Agent 2 is made in a manner similar to the synthesis described for the corresponding acid salt of Color Developing Agent 5, excepting that an equimolar amount of arbromobutyl methyl ether is used in place of 2- bromoethyl methyl ether.

The di-p-toluenesulfonic acid salt of Color Develop ing Agent 4 is advantageously made in a manner similar to that described for the corresponding acid salt of Color Developing Agent 3, excepting that an equimolar amount of N-ethyl-3-propylaniline is used in place of N-ethyl-3-methylaniline.

Still other color developing agents of Formula I are made using the synthesis illustrated herein using the appropriate starting materials and intermediates.

The following examples are included for a further understanding of our invention and the utility thereof:

EXAMPLE 1 EXAMPLE 2 The procedure described in Example 1 was repeated with solutions of dilferent pH values. The results are tabulated in Table 2.

EXAMPLE 3 The procedure described in Example 1 was repeated by adding the developer salt to sodium carbonate solutions of 25, or 320 g/l, respectively, to simulate actual color developer solutions. The results are tabulated in Table 3.

EXAMPLE 4 The procedure described in Example 1 was repeated by adding the developer salt to solutions with 50, 100 or 150 g/l NaPTS. The results are summarized in Table 4.

EXAMPLE 5 The procedure described in Example 1 was repeated by adding the developer salt to a solution with g/l NaPT S. The results are given in Table 5.

TABLE 1 Solubility at pH 10 R R2 G./l. M

CzHs H 26 1 C235 CH: 19 1 C2H4OH H 90 32 CzHtOH CH: 90 3 2H4OH CH; 650 1. 2 CHzCHOHCHzOH CH: 490 9 CzHiO CH3 CH: 690 1. 3 CzHtO CH: CH: 84 2 PTS: p-tolueno sulfonlc acid. (Jim R! "NBA: Lil-naphthalene dlsulfonlc acid. \N/

7 8 TABLE 2 Table 2: Small changes in pH (pH 10 1': l or 2 units) have little influence on the above results. solubilities at other Table 3: Higher concentrations of inorganic salts in Developer San pH g M the solution decrease the solubility of pphenylenediamines substantially, both for the inorganic c mso 1 1.7 -95 .34 and the PTS acid salts of the developing agents. 5 g :1; 5 -gg Table 4: The solubility of p-phenylenediamines with O L] inorganic counteracldscan be increased by adding Na- TABLE 3 Solubility in Na CO Solution (g Na CO JIiter solution) Developer 7 Salt 25 I00 320 c H280, "-95 /l (.3M) l6g/l (.06M) -2 /l (.007M) F 2 PTS -700g/l (1.3M) -700g/l (1.3M) -l50g/l (.3M)

TABLE 4 PTS to the solution. In the given example this increase is approximately 8 fold when 150 g/l NaPTS have been Nu PTS Solubility f added to the solution. added 10 the Solution Developer B Salt) Table 5: Addition of NaPTS to solutions which al- 0 19 8/ 01M ready contain the PTS salt of a p-phenylenediamine is 50 g/| 20 g/[ M not desirable. The solubility decreases. The PTS intro- I00 8/ 40 8 02M duced with the developing agent obviously is sufficient 150 N 067M to give the effect of increased solubility.

' V A The following Example 6 will serve to further distinguish the method and compositions of the present in- TABLE 5 vention from those of the prior art.

EXAMPLE 6 Na P'TS Solubility of added to the solution Developer F (PTS Salt To simulate an actual working developer solution solubility measurements were obtained by adding the developer or salt in weighed portions to a known volume of pH 10 phosphate buffer (11 0.75) to which had 8 238 63m been added 2 g/l of Na sO The mixture was stirred until solution was obtained (absence of scattered light) Room temperature; pH 10.0 I 0 and the adjusted back to addition of (pellets). This process was repeated until a portion of The data in Tables l-5 show: the compound no longer dissolved. A repeat of the test Table l: The evaluated p-phenylenediamines with inusing smaller portion additions near the solubility limit organic (and some organic) counteracids have a soluestablishes the solubility of the compound under these bility in water (room temperature, pH 10) of about 0.1 4 conditions. Storage of the solutions for several days at to 0.3mol/l, whereas the PT S salts show solubilities of room temperature insures against supersaturation. The approximately 1.0 mol/l. Differences in the structure of data shown in Table 6 represent the average of 3-4 repthe color developer are of minor importance. WM licate s. J

TABLE 6 Solubility in M/l. (of solvent) g./1. (of solvent) CUHsSOgH 2,5-(CH )zCtH SOzH Aromatic primary amine Free base H01 salt salt PTS salt salt H5C2NC2H5 0.08 (18. 9) 0.14 (72) CH Nl z H C2NC2H4OCHa 0.03 (5. 2) 0.10 (50.9) 3.17 (1751) 0.83 (479) The foregoing Table 6 clearly demonstrates that in each case the PT S salt of the primary aromatic amine was more soluble than one or more of either the free base, the inorganic acid salt, the benzene sulfonate salt of U.S. Pat. No. 2,618,558 or the closely analogous 2,5- (CH3 )2C6H3SO3H.

Thus, it should be clear that use of the FT S salts of p-phenylenediamine developing agents, preferably those of the type defined by Formula ll, and even more advantageously those of Formulalll, above permits dissolution of substantially larger quantities of developing agent in a given amount of solvent than has heretofore been possible.

The utility of the PTS salts described hereinabove and of the aqueous alkaline solutions prepared therefrom in photographic processing systems will be readily recognized by those skilled in the photographic arts, however, concrete examples of this utility as well as the advantages which can be achieved when specific members of the class of p-phenylenediamine are used as developing agents are presented in the aforementioned copending US. Pat. Applications Ser. Nos. 94,992 and 94,993 which have been incorporated herein by reference.

Generally, these organic acid salts of pphenylenediamine developing agents will be used in aqueous alkaline solution at a pH above about 8 and preferably above about 9.5. The concentration of the salt present in the solution will be dependent upon the concentration of developing agent which is required. Generally, this concentration will range from about 0.5 to about g/] in working developer compositions depending upon the particular system to which the developer is to be applied. However, in concentrates suitable for shipping and dilution prior to use as working developers, the concentration of PT S salt is limited only by its own solubility and the stability of such a solution under a given set of conditions of storage and shipping. Thus, in working solution the concentration of the PTS salt is limited by the use to which the solution is to be put and hence the amount of developer which it is sought to have present therein. Theoretically, at least insofar as the specific color developing agents described in Formula ll hereinabove are concerned, the problem of color developer solubility no longer exists since the limits of the solubility of the FT S salts of these materials are generally at or well above the practical concentration limits for those materials in working solutions.

As demonstrated by the foregoing examples the instant invention demonstrates the following distinct advantages:

A. p-phenylenediamines with p-toluenesulfonic acid (PT S) counteracid have a considerably higher solubility than the same compounds as free bases which are highly unstable and dissolve poorly or as salts with other organic or inorganic counteracids which have only slightly improved solubility;

B. the addition of sodium benzene sulfonate at the levels taught in US. Pat. No. 2,618,558, i.e. -200 g/l increases the solubility of the model compounds from 0.007 mole/l to 0.035 mole/l for the highest concentrations of benzene sulfonate (data derived from US. Pat. No. 2,618,558). Using the PTS salt of pphenylenediamine increases the solubility to more than 1 mole/l implying that together with the developing wherein n is either 1 or 2; R, and R, are lower alkyl, hy-

droxy lower alkyl, or alkoxy lower alkyl and R is lower alkyl or lower alkoxy have unexpectedly high solubility in aqueous alkaline solutions of the type utilized for the color development of color photographic elements and that hence they possess all of the above-described advantages incident to such unusually high solubility.

Solutions of these materials can of course include all of the addenda incident to developer compositions of the type described including but not limited to color developer stabilizing agents, alkali metal chloride, alkali metal bromide, sulfite ion and the alkali metal salts of weak acids.

Solutions of the PT S salts of the color developers described by Formulas I and II are formed simply by dissolving the same in an aqueous alkaline solution. Generally the working developer solutions can comprise up to about 200 g/l of color developing agent although much lower concentration levels on the order of from about 0.5 to about 15 g/l will provide satisfactory results in conventional processes as mentioned above. Concentrations above this level are useful when it is sought to speed up the development rate and/or to increase the throughput capability of the developer bath. Thus, in conventional practice, concentrated aqueous alkaline solutions of the PT S salts of the developing agent, i.e. those solutions having concentrations above about 200 g/l will generally be prepared for shipping and storage. These concentrates may contain as much of the salt as tolerable in the particular system so that precipitation or phase separation does not occur. When received by the consumer-processor these concentrates will be diluted with water to provide working solutions with color developer agent concentration of up to, for example, perhaps 200 g/l. The concentrate will generally contain a sufficient amount of alkali i.e. sodium, potassium or ammonium hydroxide or sodium 0r potassium carbonate to provide when dissolved in water to yield the desired developing agent concentration, a solution of the developing agent which has a pH above about 8 and preferably above about 9.5.

Since the active developing agent of working developer solutions prepared from such concentrates are pphenylenediamine developing agents they will include small amounts of sulfite ion which stabilize the developing agent against aerial oxidation during storage as a concentrate and while in use as a working developer solution.

Furthermore, in addition to the other addenda such as benzyl alcohol, (0-15 ml/l) alkali metal chlorides (0-15 g/l), alkali metal bromides (0.1-1.0 g/l), alkali metal or ammonium sulfite (0.1-5.0 g/l) and alkali metal or ammonium salts of weak acids (10.0-50.0 g/l) which are conventionally present in pphenylenediamine developer solutions of this type in the concentration ranges shown in parentheses, it is generally desirable to incorporate a stabilizer composition which insures that the developer does not separate into phases at levels of from about 0.1 to about 5.0 g/l. Two such stabilizers are hydroxylamine sulfate and dihydroxyacetone. 7

Once working developer solutions of the novel PTS Salts of p-phenylenediamine developing agents described hereinabove are prepared, their use is in the conventional fashion well known to those skilled in the art. In brief the color development of a multilayer silver halide color emulsion layer is accomplished by contacting the silver halide with an aqueous alkaline solution of a p-phenylenediamine developing agent in the presence of a coupler that reacts with oxidized developing agent to form a dye. In accordance with the present invention the improvement in such a process comprises using the p-toluenesulfonic acid salt of the pphenylenediamine developing agent as the developing agent to provide higher concentrations of developing agent than would normally otherwise be possible. It is of course possible to use these salts to obtain conventional levels of developer concentrations the advantage in such usage being the ease with which dissolution is achieved and the certainty that these materials will remain in solution at these relatively low concentration levels in view of their extremely high solubility in aqueous alkaline solvent systems.

The invention has been described in detail with specific reference to preferred embodiments thereof; however, it should be understood that variations and modifications can be effected within the spirit and scope of the invention and that the same should not be limited except as specified in the appended claims.

I claim:

lQAn aqueous alkaline photographic color developing solution containing, as the color developing agent, a p-toluenesulfonic acid salt which is highly soluble in aqueous alkaline solutions, said p-toluenesulfonic acid salt having the formula:

atoms.

2. The photographic color developing solution of claim l'wherein said p-toluenesulfonic acid salt has the formula:

wherein m is an integer having a value of from 2 to 4,

R is an alkyl group of l to 4 carbon atoms and R is a member selected from the group consisting of alkyl groups of l to 4 carbon atoms and alkoxy groups of l to 4 carbon atoms.

3. The photographic color developingsolution of claim 1 wherein said p-toluenesulfonic acid salt is a di-p-toluenesulfonic acid salt of a member selected from the group consisting of:

l N-Ethyl-N-methoxyethyl-3-methyl-pphenylenediamine;

. N-Ethyl-N-methoxybutyl-3-methyl-pphenylenediamine; N-Ethyl-N-ethoxyethyl-3-methyl-pphenylenediamine; N-Ethyl-N-methoxyethyl-3-n-propyl-pphenylenediamine; 'N-Ethyl-N-methoxyethyl-3-methoxy-pphenylenediamine; and

. N-Ethyl-N-butoxyethyl-3-methyl-pphenylenediamine. 4. The photographic color developing solution of claim 1 further including a stabilizing amount of a water-soluble sulfite. 5. An aqueous alkaline photographic color developing solution containing, as the color developing agent, the di-p-toluenesulfonic acid salt of N-ethyl-N- methoxyethyl-3-methyl-p-phenylenediamine.

' 6. In a process of color developing a photographic element by contacting said element with an aqeuous alkaline solution of a salt of a p-phenylenediamine color developing agent in the presence of a coupler that reacts with oxidized color developing agent to form a dye, the improvement wherein said salt is a p-toluenesulfonic acid salt of the formula:

l lHz wherein m is an integer having a value of from 2 to 4,

R, is an alkyl group of l to 4 carbon atoms and R is a member selected from the group consisting of alkyl 13 14 groups of 1 to 4 carbon atoms and alkoxy groups of 1 4. V N-Ethyl-N-methoxyethyL3-n-propyl-pto 4 carbon atoms. phenylenediamine;

8. The process of claim 6 wherein said salt is a 5, N-ethyl-N-methoxyethyl-3-methoxy-pdi-p-toluenesulfonic acid salt of a member selected phenylenediamine; from the group consisting of: 5 and l N-Ethyl-N-methoxyethyl-3-methyl-p- 6. N-Ethyl-N-butoxyethyl-3-methyl-pphenylenediamine; phenylenediamine. 2. N-Ethyl-N-methoxybutyl-3-methyl-p- 9. The process of claim 6 wherein said salt is the phenylenediamine; di-p-toluenesulfonic acid salt of N-ethyl-N- 3. N-Ethyl-N-ethoxyethyl-3-methyl-p- 10 methoxyethyl-3-methyl-p-phenylenediamine.

phenylenediamine;

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent No, 3,816,134 Dated June 11, 1974 Inventor(s) Dietmar Schellenberg, et a1 It" is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The term of this patent subsequent to April 25, 1989,

has been disclaimedo Signed and Scaled this [SEAL] Arrest:

RUTH c; msbu 4 c. MARSHALL DANN Arresting Officer Commissioner oj'Palems and Trademarks Twenty-fourth of August 1976 

2. The photographic color developing solution of claim 1 wherein said p-toluenesulfonic acid salt has the formula:
 2. N-Ethyl-N-methoxybutyl-3-methyl-p-phenylenediamine;
 2. N-Ethyl-N-methoxybutyl-3-methyl-p-phenylenediamine;
 3. N-Ethyl-N-ethoxyethyl-3-methyl-p-phenylenediamine;
 3. N-Ethyl-N-ethoxyethyl-3-methyl-p-phenylenediamine;
 3. The photographic color developing solution of claim 1 wherein said p-toluenesulfonic acid salt is a di-p-toluenesulfonic acid salt of a member selected from the group consisting of:
 4. N-Ethyl-N-methoxyethyl-3-n-propyl-p-phenylenediamine;
 4. N-Ethyl-N-methoxyethyl-3-n-propyl-p-phenylenediamine;
 4. The photographic color developing solution of claim 1 further including a stabilizing amount of a water-soluble sulfite.
 5. An aqueous alkaline photographic color developing solution containing, as the color developing agent, the di-p-toluenesulfonic acid salt of N-ethyl-N-methoxyethyl-3-methyl-p-phenylenediamine.
 5. N-ethyl-N-methoxyethyl-3-methoxy-p-phenylenediamine; and
 5. N-Ethyl-N-methoxyethyl-3-methoxy-p-phenylenediamine; and
 6. N-Ethyl-N-butoxyethyl-3-methyl-p-phenylenediamine.
 6. N-Ethyl-N-butoxyethyl-3-methyl-p-phenylenediamine.
 6. In a process of color developing a photographic element by contacting said element with an aqeuous alkaline solution of a salt of a p-phenylenediamine color developing agent in the presence of a coupler that reacts with oxidized color developing agent to form a dye, the improvement wherein said salt is a p-toluenesulfonic acid salt of the formula:
 7. The process of claim 6 wherein said salt has the formula:
 8. The process of claim 6 wherein said salt is a di-p-toluenesulfonic acid salt of a member selected from the group consisting of:
 9. The process of claim 6 wherein said salt is the di-p-toluenesulfonic acid salt of N-ethyl-N-methoxyethyl-3-methyl-p-phenylenediamine. 